1. Field of the Invention
The present invention relates generally to Transmission Control Protocol/Internet Protocol (TCP/IP)-based communications in a mobile communication system, and in particular, to an apparatus and method for increasing throughput by controlling time delay such that timeouts do not occur during TCP/IP-based communications.
2. Description of the Related Art
Since the start of their commercialization, mobile communication systems have witnessed a rapid growth and are now servicing a large number of users. Along with the development of mobile communication systems, Circuit Switching (CS) has gradually given place to Packet Switching (PS) and CS mobile communication systems now coexist with PS mobile communication systems according to their uses.
FIG. 1 illustrates the configuration of a conventional mobile communication system.
In FIG. 1, the mobile communication system includes a Core Network (CN) 140, Base Station Controllers (BSCs) 130, Base Transceiver Stations (BTSs) 120, and a Mobile Station (MS) 110.
In CS communications, the MS 110 communicates with the other party through a BTS 120, a BSC 130, and a Mobile Switching Center (MSC) of the CN 140.
Similarly, in PS communications, the MS 110 accesses the Internet through the BTS 120, a Packet Control Function (PCF) of the BSC 130, and a Packet Data Serving Node (PDSN) of the CN 140 and communicates with the other party.
The PDSN is a kind of a router for connecting the Internet to the mobile communication system. The PCF may reside inside or outside the BSC 130 depending on system implementation.
Generally, the PS communications are conducted in a connection-oriented or connectionless-oriented manner. The TCP/IP is connection-oriented and the User Datagram Protocol/Internet Protocol (UDP/IP) is connectionless-oriented.
In operation, when one end node sends a packet to a second end node in the TCP/IP, the second end node sends a response message in case of successful packet reception. This way, the communication connection status is checked during communications.
However, in case of a failed packet reception, due to packet loss or a long time delay, the second end node does not send a response message. Thus, a timeout occurs for the transmitted packet in the TCP/IP layer of the end node and the end node significantly reduces the amount of data to be sent at a time, considering that the network is congested. The decrease of the data amount leads to the decrease of throughput and performance degradation.
Typically, during handover of the MS 110 in the mobile communication system, a long time delay often occurs in a packet transmission, resulting in frequent timeouts.
Conventionally, an intermediate node (usually, a BSC) imposes a random delay on a received packet and then forwards the packet to the other party. The constant delay lengthens the timeout duration and, thus, prevents the decrease of throughput.
However, a time delay imposed during handover adds to a total time delay too long to be tolerated in the TCP/IP because the handover involves a time delay in itself. Consequently, the decrease of throughput is not prevented, and, conversely, the number of timeout occurrences is increased.